Wireless telephone system



Nov. 27, 1928.

M. w. STERNS WIRELESS TELEPHONE SYSTEM 2 Sheets-Sheet Filed Jan. 24, 1925 M. W. STERNS WIRELESS TELEPHONE SYSTEM Nov. 27, 1928.

File n- 24, 1925 2 Sheets-Sheet, 2

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Patented Nov. 27, 1928. I

OFFICE.

MORTON W. STERNS OF JAMAICA, NEW YORK.

WIRELESS TELEPHONE SYSTEM.

- Application filed January 24, 1925. Serial No. 4,397;

My invention relates to a radio or guided radio system or apparatus for simultaneous sending and receiving. The main object is to provide for apparatus which can be used in a manner substantially as simple as the ordinary wire telephone so that two parties can carry on a conversation together and without interruption such as is occasioned by the use of hand orautomatic switches.

Another object is to provide simple and compact apparatus which can be used for either transmitting or receiving or both.

Another object is to provide for maximum power effect with a simple circuit and small expense of apparatus.

Another object is to utilize the same vacuum tube or tubes for transmission'as well as reception.

In its preferred form the invention contemplates the use of a three-electrode tube or oscillation device with the anode or output circuit inductively connected with the aerial or loop. In my original application No. 354,611, filed January 28, 1920, PatentNo. 1,524,413, January 27, 1925, I have claimed the invention broadly and also specifically claimed one form in which the anode is direct: 1y connected to the aerial. This application is a partial division from said former application. This case also involves improvements for high power work with a filter to cut out generator hum and an, amplifier for weak signals. I r

Fig. 1. is a diagrammatic view of one ar rangement of apparatus or circuit embodying the improvements of my invention.

Figs. 2, 3 and 4 are similar diagrammatic views showing other modifications of my invention. i

Fig. 5 shows an improved high power circuit.

I have shown diagrammatically a typical telephone transmitter 5, receiving device, 6. aerial or antenna loop 7, and an oscillation device 8. i 7

In the preferred form the oscillation device is a vacuum tube having a filamentary cathode 9 with the usual battery and adjustable resistance, an anode or plate 10, and a control element or grid 11.

The primary coil 12 of the telephone receiver transformer and the source of power, in this instance a battery 13, are connected in series between the filament circuit and the plate. The secondary coil ofthe telephone transmitter transformer is connected between the grid and the filament. Obviously the transmitter i and receiver may be located at some distance from the remainder of. the set, if desired, and operation carried on by remote control.

The loop circuit includes the tuning capacity 15 and inductance 16, the latter being variably coupled with the coil 17 which is connected to the oscillation device. In this case one end of the coil 17 is connected by a lead 18' to the plate 10 and the other end of the coil is connected to, the'grid but with a condenser 19 interposed. The variablecapacity 20'is connected between the grid and the plate through the condenser 19. A capacity 21 is also interposed between the grid and the filament through thecondenser 19, and a capacity 22 between'the filament and plate.

The resistance of the secondary 14 of the telephone transmitter should be kept low enough, so as to maintain the grid 11 at the same potential as the negative end of the filament, that is, low enough to prevent the grid from collecting a. positive charge. Theimpedance of the secondary of the modulation transformer orinduction coil should equal the input impedance of the tube or tubes, or the impedance between the grid and the filament. Furthermore the impedanceof theprimary of the transformer should equal the impedance of the transmitter, buzzer or other alternating current source. The ratio ofthe primary to the secondary should be large so as to impress a high potential on the grid.

On the other hand, in the plate or power circuit the in'ipedance of the primary should equal the impedance of the circuit into which it is inserted], and the impedance of the secondary should equal theimpedance of the circuit into which'it feeds, such as a receiver or amplifying device. A strong D. C. which supplies power to the plate circuit will not affeet the receiving device, but any Weak A. C. effect, such as received signals or your'own voice inthe transmitter, will affect the receiving' device.

Referring to Fig. 1 as a typical embodiment of my invention the operation is as follows: v

The battery 13 supplies energy to the anode 10 of the vacuum tube 8. On account of the feed back condensers2l and 22 the tube 8 by the adjustment'of the condenser 20. The

' hear h'is'own voice,

inductance 17 maybe coupled to a tuned'loop as showniniFig. 1 or to an inductance 1ncluded'in circuit with a tuned antenna system (as in Fig. 3)., The telephone transmitter 5 acting through the modulation transformer 14 varies the potential, with respect to the filament, of the'grid 11 and hence "modulates the amplitude of said oscillations substantially in accord with the voice frequency applied to the transmitter 5, thus causing the system to act as'a radio telephone transmitter.

On the other hand, an electromagnetic wave of resonant frequency impinging on the antenna system will vary the potential of the grid 11 and henceyary the current flowing through the primary of the telephone transformer 12 thus producing audible signals in the'telephone receivert whose magnitude will vary substantially as the magnitude of the impinging wave, thus causing the system to act'as a radio telephone receiver.

In practice, two or more stations would be tuned to the same frequency, reception being accomplished by the homodyne or Zero beat principle so that no heterodyne note would be produced. It is obvious then that if this system is used the party talking can not only similar to the familiar side talkof the conventionalwire telephone, but can be interrupted by the listener at any time in case of miunderstanding or inability,

to hear properly, thus constituting another a feature common to wire telephony but not to single channel radio telephony heretofore.

- WVi-th the foregoing apparatus it is possible to simultaneously transmit'and receive on the same aerial and with the same wave length and the same tube without the use of any switches, the operators at'the opposite ends of such a system talking and listening at the same time as on ordinary wire lines.

In case station A wishes to speak telephonically with station B, station A will say, Hello B, Hello B, A calling, A calling, answer please. Station B on hearing A will tune to As wavelength automatically as that is the point of loudest and clearest speech reception. If B now speaks to A, A will hear him, as he is tuned to the same wave length as B, due to the previousoperations. It is evident therefore that A can break in on B, or vice versa, at any instant and ask fora misunderstanding or for any other purpose andwithout throwing any switches. This circuit will therefore give all the advantages of and ordinary land line telephone with. the added advantageo'fthe peculiarly clear speech which is a well known advantage of the radio telephone.

The connections of the filament and plate to the aerial may be transposed, but in any case the positive of the source of power 13 shouldbeconnected to the plate. 1 The'plate andgridconnections to the'aerial may also be transposed. A receiving device maybe inserted in or coupled with the source of power. The plate may be directly connected to the aerial, as in the parent application. The grid may also be directly connected to the aerialbut with a condenserinterposed. In low power systems the telephone instruments may be inserted directly in the circuits, as shownin my earlier application. 7

In 2 I have shown an aerial 25 grounded at 26 and provided with avariable inductance 27 which is coupled with the grid and plate circuits by means'of thee-oils .28 and 29. In this case it will be seen that the telcphone'receiver is also connected between the plate and the power source- In the arrangement of Fig. 3 the transmitting and receiving circuits are inductively coupled with the aerial by means of the coil 30 which is connected on opposite: sides of the condense-rs 31 and 32, the latter being interposed between the grid and filament, and the plate and filament, respectively.

In the arrangement shown in Fig. 4 the aerial has avariable inductance 83 and capacity 34, and the grid and plate are inductively coupled through the coils 33 and 35. In this case the telephone receiver 6 is connected directly to. the power circuit, but the transmitter is connected between the grid and filament, as in the previously "described arrangement. It is obvious that the receiving device can also be inductively connected to the power source if desired.

In the arrangement shown-in Fig. 5 there are two tubes 8 and 8 in parallel and agenerator 13. I have also shown a radio frequency by-pass 36, a filter 37, and an amplitier 38 connected'to the receiving phone 89 presumably located at some distance away. I have also shown an amplifier etO in the circuit leading to the transmitter microphone 41 or other longdistance line (not shown). In this case theloop 7 replaces the coil17 so that the loop is directly connected in the circuit. a V V Such an arrangement can be used for simultaneous broadcasting and reception] From the above it canbe seen that the transmitting and receiving device can be added to any oscillating circuit if proper precautions are taken to place them in their proper places as shown. in the examples above.

It will be, seen from the foregoing that according to my invention no separate receiving set is required. All the tubes serve as oscillators and yet produce results which in ordinary sets would require aismany'modiu lators as oscillators. For instance according to my invention we can use four-oscillators in place of two'oscillators and two'modulators thus doubling the power of the set.

I'claimz,

1. Ina singler'adioset for both transmis Inc oscillation generator having a cathode, an anode, and a control element, said anode and said control element being connected by a circuit including a control element condenser and a tuning inductance, said tuning inductance being magnetically coupled to said antenna system, said control element having a modulating device included in its associated circuits and said anode having a telephone receiving device connected in its associated circuits. 7

2. In a single radio system for both trans mission and reception, an antenna system which is used as both a radiator and an absorber Without change of circuit connections, an oscillation generator having a cathode, an anode, and a control element, said anode and said cathode being connected by a circuit including a control element condenser and a tuning inductance, said tuning inductance being magnetically coupled to said antenna system, said control element having a modulation device connected in its associated circuits and said anode having a telephone receiving device connected in its associated circuits.

3. In a single radio syiem for both transmission and reception, an antenna system, a vacuum tube having an anode, a cathode, and a control element, said anode being connected to said control element by a circuit including a control element condenser and a tuning induct-ance, said inductance being magnetically coupled to said antenna system, said vacuum tube having associated circuits such that it may function as either a voice modulated oscillator or a homodyne detector.

4. In a single radio system for both transmission and reception, a single antenna system which may be used for both radiation and reception without alteration of any circuits comprising said system, an oscillation device having a cathode, an anode, and a control electrode, a circuit including a control element condenser and a tuning inductance connecting said anode and said control electrode,

said inductance being coupled to said antenna system, a telephone transmitter connected to the primary of a modulation transformer the secondary of said modulation transformer being connected between said cathode and said control element, and a telephone receiving device whose circuits are associated with said cathode.

5. In a single radio system for both transmission and reception, a single antenna system which may be used for both radiation and reception without alteration of any circuits comprisingsaid system, an oscillation device having a cathode, an anode, and a control electrode, a. circuit connecting said anode and said control electrode, said circuit ineluding a control element electrode and a tuning inductance, said inductance being coupled to said antenna system, a telephone transmitter connected to the primary of a modulation transformer, the secondary of said modulation transformer being connected between said cathode and said control element, and a telephone transformer whose primary is in series with a direct current source and connected between said anode and said cathode, the secondary of said transformer being connected to a telephone receiver.

MORTON W. STERNS. 

